A motor drive of an embodiment of the present invention includes a PWM converter for converting AC power inputted from a low voltage AC power source into DC power by PWM control, an inverter for converting the received DC power to AC power to drive a motor, and a capacitor connected between the PWM converter and the inverter. The PWM converter is operated so as to limit input and output currents or input and output power to predetermined values, and supplied from the low voltage AC power source with a lower voltage than a voltage required to drive the motor. The PWM converter boosts a DC link voltage being an output voltage to the voltage able to drive the motor, and thereby serves to increase the potential difference of the capacitor between charged and discharged states to reduce the capacitance of the capacitor.
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1. A motor drive comprising: a PWM converter configured to convert AC power inputted from a low voltage AC power source into DC power by PWM control; an inverter configured to receive the DC power and converting the DC power into AC power to drive a motor; a capacitor connected between the PWM converter and the inverter; an input voltage detector configured to detect an AC voltage supplied from the low voltage AC power source to the PWM converter; an input current detector configured to detect a current to be inputted from the low voltage AC power source to the PWM converter; and an output voltage detector configured to detect a DC voltage converted by the PWM converter, wherein the PWM converter is operated so as to limit input and output currents detected by the input current detector or input and output power detected by the input voltage detector, the input current detector and the output voltage detector to predetermined values, wherein the PWM converter is supplied from the low voltage AC power source with a minimum voltage within a voltage range required to drive the motor or an AC voltage having peak value lower than the minimum voltage, and wherein the PWM converter boosts a DC link voltage, which is an output voltage, to the voltage able to drive the motor, to reduce the capacitance of the capacitor.
A motor drive system uses a PWM converter to transform low-voltage AC power to DC, and an inverter to change the DC power back to AC to drive a motor. A capacitor is placed between the converter and the inverter to smooth the DC voltage. The system measures the input AC voltage and current, and the output DC voltage of the converter. The PWM converter limits input/output current or power based on these measurements to pre-set levels. The converter operates from a low-voltage AC source (either within the motor's voltage range or with a peak value lower than the minimum required motor voltage). The PWM converter boosts the DC voltage (DC link voltage) to the level needed by the motor, which allows for a smaller capacitor to be used.
2. The motor drive according to claim 1 , wherein the PWM converter includes: a monitoring unit configured to monitor the voltage of the capacitor; and an alarm unit configured to issue an alarm to stop the motor, when the voltage of the capacitor is equal to or less than a certain value higher than an input voltage peak value, in order to protect the PWM converter from an overload.
The motor drive system described in claim 1 includes a capacitor voltage monitoring unit and a safety alarm. The monitoring unit observes the voltage of the capacitor situated between the PWM converter and the inverter. If the capacitor's voltage drops to a certain level (higher than the input voltage peak value), indicating a potential overload, the alarm unit activates and shuts down the motor. This safeguard prevents damage to the PWM converter from the overload condition caused by an under-voltage capacitor. This enhances system reliability and prevents converter failure.
3. The motor drive according to claim 1 , wherein a smoothing capacitor is used instead of the capacitor.
The motor drive system described in claim 1 replaces the capacitor connected between the PWM converter and the inverter with a smoothing capacitor. The fundamental functionality remains the same: the smoothing capacitor is used to filter and stabilize the DC voltage between the PWM converter and the inverter before it's converted to AC for the motor. This substitution offers a different implementation choice for DC voltage smoothing, potentially affecting cost, size or performance compared to a standard capacitor but retaining the core PWM conversion and inversion process.
4. A motor drive comprising: a PWM converter configured to convert AC power inputted from an AC power source into DC power by PWM control; an inverter configured to receive the DC power and converting the DC power into AC power to drive a motor; a capacitor connected between the PWM converter and the inverter; a step-down transformer connected between the AC power source and the PWM converter; an input voltage detector configured to detect an AC voltage supplied from the step-down transformer to the PWM converter; an input current detector configured to detect a current to be inputted from the step-down transformer to the PWM converter; and an output voltage detector configured to detect a DC voltage converted by the PWM converter, wherein the AC voltage is within a voltage range required to drive the motor, wherein the PWM converter is supplied from the step-down transformer with a lower voltage than the voltage of the AC power source, wherein the PWM converter is operated so as to limit input and output currents or input and output power to predetermined values, and wherein the PWM converter serves to reduce the capacitance of the capacitor.
A motor drive system includes a PWM converter, an inverter, and a capacitor connecting them. A step-down transformer lowers the voltage from an AC power source before it reaches the PWM converter. Input voltage and current detectors measure the voltage and current from the transformer to the converter, while an output voltage detector monitors the DC voltage after conversion. The AC voltage supplied to the PWM converter (after step-down) is within the range needed to drive the motor. The PWM converter limits the input/output current or power to specified values. By using the step-down transformer to lower the initial AC voltage, the system reduces the required capacitance of the capacitor between the converter and inverter.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
January 28, 2016
September 19, 2017
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